Site Loader
Rock Street, San Francisco

Dirt is inhabited by 1000s of different species of micro-organisms Torsvik and Ovreas 2002. Bacteria, archaea Fungi, and protists are all found in dirt and play critical functions to the dirt environment ( Willey et al. 2008 ) . The diverseness in dirt microbic communities seems to be greater than those found in most aquatic environments ( Willey et al. 2008 ) . Soil bacteriums are indispensable for the biogeochemical rhythms affecting N, C, S, Fe, and manganese ( Willey et al. 2008 ) . Microbial communities degrade and recycle organic stuff doing dirt formation and alimentary cycling ( Willey et al. 2008 ) . The activity of microbic life in dirts is related to works life in an dirt environment ( Willey et al. 2008 ) . Merely a little figure of the bacteriums populating in dirt will bring forth growing on microbiological media hence growing media choice is critical to isolation of bacterial civilizations ( Davis et al. 2004 ) .

The aim of this survey was to insulate assorted populations of micro-organisms from a wood dirt sample utilizing multiple culturing techniques. Upon isolation of settlements a pure civilization was to be obtained and processed through assorted biochemical trials to find the individuality of a individual bacteria in the dirt.


As outlined in Robertson and Egger ( 2009 ) , the experiment required a forest dirt sample of 1 gm to be suspended in 99 millilitres of deionized H2O. Consecutive dilutions from 10-2 to 10-7 were made with the dirt sample and so cultured on unfertile media utilizing sterile technique. Enumeration was done on the bacterial dirt dilutions to get Colony-Forming Units. Streak plate sub-cultures were made from the settlements in order to obtain pure civilizations. A choice of a distinguishable bacterial settlement was made and examined for morphology and Gram stain proving. The bacterial isolate was studied for environmental effects on growing by sub-culturing it onto media of assorted temperature, pH and solute concentration. Starch hydrolysis, H sulphide production, motility, ammonification, nitrification, denitrification and catalytic activity were biochemical trials conducted on the bacterial isolate to separate its engagement in cycling of C, N and S.


The isolation of bacterial settlements for a assorted population of micro-organisms found in the forest dirt resulted in the settlement morphology outlined in Table 1. The settlements observed were conspicuously irregular in signifier and rose off the media ( Table 1 ) . The settlements were glistening xanthous ( Table 1 ) . The scrutiny of individual bacterial cells under microscope demonstrated individual B agreement ( Table 1 ) . The bacillar bacterial cells were about 4 microns in length ( Table 1 ) .

Table 1. Colony and cellular morphology of bacterial isolate from forest dirt 10-4 civilization.

Colony and Cellular Morphology










Optical Property






Diameter ( millimeter )

1.5 millimeter

Cell form at 1000x magnification


Cell agreement

Single B

Cell dimension

4 & A ; Icirc ; ?m

The stray dirt bacterial civilization was notably gram positive when examined under microscope on the prepared slide ( Table 2 ) . The sum-up of biochemical trials found in Table 2 show the bacteria to be motile, catalase positive, incapable of starch hydrolysis or denitrification but able to execute nitrification ( Table 2 ) .

Table 2. Biochemical trial consequences of forest dirt 10-4 bacterial isolate.


Consequences and Observations

Gram discoloration


Starch hydrolysis

Negative, black with I

Hydrogen sulphide H2S decrease

Negative for H2S production




Small sums

Denitrification ( NO3- to NO2 )


Denitrification ( NO3- to NH3 or N2 )

N/A no denitrification of NO3- to NO2-

Nitrification ( NH3/ NH4+ to NO2- )


Nitrification ( NH3/ NH4+ to NO3- )




Optimum temperature

37 & A ; Acirc ; & A ; deg ; C

Optimal pH / pH categorization

pH 9 / alkalophile

Optimal salt concentration

0 %


The bacteria isolated from the forest dirt sample could be Curtobacterium. This genus of bacteriums is distinguished by its irregular rods and gm positive nature ( Sneath et al 1986 ) . It is possible for Curtobacterium to be confused with the genus of Cellulomonas ( Sneath et al 1986 ) . Both these genera are gram positive, irregular rods, positive for catalase activity, demonstrate motility and found in dirt environments ( Sneath et al 1986 ) . These genera do non hold a common O usage since Curtobacterium are purely aerobic while most strains in Cellulomonas are facultatively anaerobiotic ( Sneath et al 1986 ) . There are differences in menaquinone, polar lipoid and fatty acerb composing between Curtobacterium and Cellulomonas every bit good.

The biochemical trials that most strongly aided the designation of the stray bacteria included the gm staining, amylum hydrolysis, motility, catalase activity, and the temperature consequence on growing. Morphology of both the settlements and cellular degrees impacted the designation procedure. The cell agreements and dimensions obtained through scrutiny of the bacteria aligned with those listed in Bergey & A ; acirc ; ˆ™s Manual of

Systematic Bacteriology ( Sneath et al 1986 ) .

The natural home ground for Curtobacterium is works and dirt environments ( Dworkin and Falkow 2006 ) . This genus is known to rule microbic communities of grass mulching and decaying litter ( Dworkin and Falkow 2006 ) . Curtobacteria has been isolated from workss, herbs, bushs and trees which indicates that it must hold a assortment of maps within workss and dirts ( Dworkin and Falkow 2006 ) . It can be inferred that this genus has alimentary cycling capablenesss.

Further testing could be done to assistance in the designation of bacterial isolates. Possible trials could include menaquinone composing, lipid and fatty acid composing, urease production and cell wall peptidoglycan belongingss ( Sneath et al 1986 ) . This survey did non deeply look into the O usage of the bacteriums but farther testing of this feature could be utile in placing both genus and species. A polymerase concatenation reaction ( PCR ) elaboration can be used to sequence DNA and detect micro-organisms that may be hard to insulate in vitro, nevertheless this can be a really expensive biochemical trial ( Picard et al. 1992 ) .

The consequences obtained could hold been erroneous from a figure of beginnings. Improper isolation of settlements is a possibility as run home bases to obtain pure civilization may hold been contaminated. In proving motility it was indispensable to inoculate the angles right otherwise the consequences may go invalid. The trials performed offer some distinguishing features but tend to miss item, for case the bacteriums isolated was gram positive but really small information about the constituents of its cell wall and peptidoglycan composing was found.

Post Author: admin